A semen analysis helps determine if a man has a fertility problem.
When a couple wants to conceive a child and encounters difficulty, a first step in dealing with the problem is to determine if the woman, the man or both might have reduced fertility. For the man, a semen analysis gives the doctor a great deal of information about the function of his reproductive organs. Its results can help determine the best course of action for the couple.
Semen is the white to gray fluid that is expelled from the urethra when a man ejaculates. It usually contains millions of sperm from the testis, along with fluid made by several glands. These include the seminal vesicles, 2 structures found on either side of the bladder's base, and the prostate gland, which surrounds the uppermost part of the urethra, plus a small contribution from several other glands. The seminal vesicles normally contribute at least 1/2 of the fluid in semen, with most of the remainder coming from the prostate and a small amount of fluid that accompanies sperm as they leave the testis.
A doctor orders a semen analysis to evaluate whether a man's semen contains sperm in sufficient numbers to achieve conception, and whether the sperm appear normal and move actively. A technician uses a microscope to count sperm directly in a portion of the sample, to provide a measure called the sperm count. If fewer that 40 million sperm are present per ejaculate, or about 20 million sperm per 1 mL of semen, this can cause infertility.
Other measures of fertility include the appearance of the individual sperm, called sperm morphology, and their ability to move. For sperm to be structurally normal, the head, which contains the man's genetic material, should be of proper size and shape, and each head should be attached to a tail, the part that moves. If sample contains less than 15 percent structurally normal sperm, this can cause infertility. Also, if fewer than 50 percent of the sperm are able to swim ahead actively, movement called forward progression, this can also signal infertility.
Finally, the survival rate of sperm in the sample, called their viability, is measured by evaluating them in a special chamber over time. If fewer than 75 percent are viable, this is also a possible cause of infertility.
Normally, the amount of semen in an ejaculate is 2 to 6 mL, or about 1/2 to 1 tsp. If the semen sample contains more than 6 mL, sperm density may be too low for conception to occur. A semen analysis can also indicate if there is something abnormal about the fluid in the ejaculate, such as an improper level of acidity, or its pH. The pH should be between 7.2 and 8, and could affect sperm function if it's too high or too low.
A semen analysis also determines how many white blood cells are present in the ejaculate. If there are more than about 1 million of these cells in each 1 mL, there could be an infection in the reproductive tract, which could also interfere with his fertility.
Finally, the test can also measure components of semen added by the glands to determine if there might be a blockage in the tract keeping sperm out of the ejaculate. For example, if little or no fructose is present, this might signal a blockage near the seminal vesicles, which add this sugar to semen.
In cases where a couple encounters a problem conceiving, infertility in the man alone is the cause about 1/3 of the time, while both the man and woman have a problem causing infertility in another 1/3 of couples. In men, many possible situations can lead to infertility.
Possible causes include physical problems that interfere with sperm production or their passage into the ejaculate, a hormone imbalance that interferes with sperm production, an unrelated disorder that causes infertility as a secondary effect, or other environmental or lifestyle factors. If you are having difficulty fathering a child, discuss possible reasons and semen analysis with your family doctor or a specialist in urology to decide on the best course of action for your situation.